It is well known among civil engineers that dowel rods facilitate the connection of concrete members. Dowel rods are partially inserted into a first concrete member, such as a curb or road slab, that is to later be adjoined to a second concrete member. As the first form cures, the rods become partially embedded. When the second form is poured, the ends of the dowel rods protruding from the first form are encased by the fresh concrete of the second form and become embedded therein as it hardens. The embedded dowel rods thusly join the first and second concrete members. In the case of concrete curbing poured to be later adjoined to the road or street, dowels about 1/2 inch in diameter and about 30 inches long are inserted by half their lengths into the freshly poured curbing. When the roadway is later poured, the rods become embedded and serve to firmly fasten the roadway to the curbing.
Concrete slabs and curbing are commonly poured by slipform paving machines. Paving machines are tractors that extrude concrete slabs with cross sectional shapes determined by the shape of the auger mouth or the vertical sideforms and screed. Slipform paving machines typically extrude curbing from a set of sideforms and screed, which form the concrete into the curb shape as it is extruded. The viscosity of the concrete is such that it retains its extruded shape as the curbing machine advances.
Traditionally, the dowel rods have been inserted into the freshly poured curbing by hand. This process has several disadvantages. First, the rods may not be inserted at regular intervals, at regular heights, or to regular depths. Also, additional manpower is required, not only to insert the rods but also to finish the concrete since rod insertion after pouring causes a bulge or ripple distortion in the fresh concrete. Finally, manual insertion and finishing operations are tedious, time consuming, and inefficient utilizations of manpower resources.
There have also been attempts to design mechanized dowel rod inserters to be used with slipform pavers. These too suffer drawbacks. The prior inserters are complex, bulky and cumbersome. Also, the prior inserters are inconsistent with respect to insertion angle, depth, and spacing. Furthermore, some prior inserters have been designed to trail the paver, necessitating a finishing step for the concrete member after rod insertion. Moreover, trailing inserters cannot accommodate even moderate changes in direction or elevation of the paver. If the paver turns too sharply, the inserter will be pulled into the freshly poured concrete member. Hence, there is a need for an improved dowel rod insertion device for use with a slipform paver. A means for satisfying this need has so far eluded those skilled in the art.